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1. Field of the Invention
This invention relates to stops for mechanical joints, specifically to a compact, efficient, and comfort enhancing means for defining a position of maximum extension in a mechanical joint, which dampens free movement in the joint as maximum extension is reached. When the pin stop present invention is used in orthotic and prosthetic devices, to support a knee, it is contemplated for the joints in which the pin stop present invention is used to also have a locking mechanism that when engaged prevents further flexion in the associated joint while concurrently allowing needed extension in incremental amounts until the position of maximum extension defined by the present invention is reached. The pin stop invention comprises a free-floating piston having an interior end and a partially exposed exterior end, a resilient bumper positioned to engage the interior end of the piston during maximum joint extension, and a piston-retaining pin, all of which are contained laterally within the perimeter structure of one of the pivoting members in a mechanical joint so that the exterior end of the piston is able to engage a cross stop bushing laterally positioned within the perimeter structure of the other pivoting member in the joint when the joint is at or very near to its position of maximum extension. Applications may include, but are not limited to, use in orthotic and prosthetic devices whereby the pin stop invention would assure a larger tolerance in the range of motion provided for the locking mechanism to engage as the joint with which it is associated nears its position of maximum extension, while dampening any unwanted feeling of free movement. A secondary advantage provided by the pin stop invention in orthotic and prosthetic applications is a softer extension stop for a user. However, it is contemplated that application in any mechanical joint for which the compact configuration and/or dampening action of the present pin stop invention would provide some assistance or technical advantage, would be within the scope of the pin stop invention.
2. Description of the Related Art
Components used in orthotic and prosthetic devices should be compact and minimally obtrusive for ease of use, enhanced social acceptability, and a lessened risk of hazard or damage during use. Further, a user should not experience insecurity, discomfort, or apprehension as a result of any aspect of their performance. As a fundamental part of their construction, all mechanical joints used in orthotic and prosthetic devices, must include design features and/or apparatus that define the limits of their flexion and extension. Often, the means used for defining maximum joint extension is bulky in configuration, provides an abrupt stop for the user, and/or adds unwanted thickness dimension to the device, such as the invention disclosed in U.S. Pat. No. 5,022,390 to Whiteside (1991), wherein the means for limiting extension of the ankle joint in a device supporting a leg and foot comprises an adjustable stop, mounting block, and abutment combination positioned against the outside surface of the leg support, behind the ankle of its user. In contrast, the extension limiting means of the present invention is more compact than that in the Whiteside invention, and it is laterally contained within the perimeter structure of an associated mechanical joint where it is protected from and less likely to fail as a result of unwanted interaction with surrounding objects. Further, the present invention also assures a larger tolerance in the range of motion provided for the locking mechanism to engage as it reaches the position of maximum extension than does the Whiteside invention, providing a softer extension stop for the user and dampening of any unwanted feeling of free movement in the joint. In addition to orthotic and prosthetic use, it is also contemplated for the present invention to be used in any industrial application requiring a mechanical joint with a compact configuration or dampening action, wherein some functional assistance or an operational advantage is provided by use of such configuration or dampening capability, or combination thereof. No means for limiting the maximum extension of mechanical joints is known to have the same structure or all of the advantages of the present pin stop invention.
It is the primary object of this invention to provide a compact means for limiting the maximum extension of a mechanical joint. It is also an object of this invention to provide a means for limiting the maximum extension of a mechanical joint that is substantially positioned within the pivoting members of the joint to protect it from and make it less likely to fail as a result of unwanted interaction with surrounding objects. It is a further object of this invention to provide a means for limiting the maximum extension of a mechanical joint that assures a larger tolerance in the range of motion provided for an associated locking mechanism to engage as the joint reaches its position of maximum extension, while dampening any unwanted feeling of free movement in the joint. A further object of this invention is to provide a means for limiting the maximum extension of a mechanical joint that is a softer extension stop for the user. It is also an object of this invention to provide a means for limiting the maximum extension of a mechanical joint that is simple in design and requires little or no maintenance. A further object of this invention is to provide a means for limiting the maximum extension of a mechanical joint that is made from durable materials and is efficient in operation. It is also an object of this invention to provide an extension limiting means for mechanical joints that has sufficient strength for use in orthotic devices, such as those employed to support a human knee. It is a further object of this invention to provide a means for limiting the maximum extension of a mechanical joint that is easy and cost efficient to manufacture.
As described herein, properly manufactured, and connected between the paired pivoting members of a mechanical joint, the pin stop of the present invention provides a means for defining the maximum extension of one member of the joint relative to the other. A piston is inserted into a longitudinal bore within one of the pivoting members, where it remains laterally contained within the perimeter structure of the pivoting member on the outside portion of the mechanical joint""s pivoting axis. The piston remains free-floating within the bore, but is not freely removable from it. A cutout area or opening centrally in the piston accommodates a transversely positioned retaining pin that allows the piston a limited amount of longitudinal movement within the bore, yet retains the piston substantially within the bore, with only a small portion of the piston""s exterior end remaining exposed beyond the bore""s open end. A resilient bumper is positioned within the closed end of the bore, and engages the interior end of the piston when the pivoting members are rotated into a position of maximum extension. In this way the present invention assures a larger tolerance in the range of motion provided for an associated locking mechanism to engage as the joint reaches its position of maximum extension, while dampening any unwanted feeling of free movement in the joint. It also provides a softer extension stop for the user. When flexion occurs in the mechanical joint to which the present invention is connected, the portion of the piston extending beyond the open end of the bore can be hand-manipulated to move a fractional distance in and out of the bore, but cannot be removed from the bore unless the retaining pin is first withdrawn. Preferably the design of the mechanical joint is such that the retaining pin is not visible or accessible, unless the pivoting members are physically separated from one another. For use as a means of limiting the maximum extension of the pivoting members in a mechanical joint, the present invention must also include a component connected to the second pivoting member and configured to engage the exposed end of the piston as the joint reaches maximum extension. Such engagement means in the most preferred embodiment of the present invention is provided in the form of a cross stop bushing that is laterally contained within the second pivoting member. As the pivoting members near a position of maximum extension relative to one another, the side of the cross stop bushing that is facing the piston is moved against the exposed end of the piston, causing the interior end of the piston to move toward the closed end of the bore until it becomes firmly positioned against the resilient bumper in the bottom of the bore. When a locking mechanism, such as a ratchet assembly, is used in the joint to prevent flexion and maintain the joint in its position of maximum extension, as maximum extension is reached, the bushing, piston, and bumper all become pressed firmly against one another. After the ratchet assembly or other locking means is released and flexion occurs, the bushing becomes separated from the exposed end of the piston. The piston remains within the bore where it will be ready for subsequent engagement with the cross stop bushing, however it is again free-floating and easily movable away from the bumper. The present invention has few components, each of simple design, which can be easily and cost efficiently manufactured and assembled. When the piston and cross stop bushing are made from stainless steel, the pin stop invention is durable and has sufficient strength to provide proper support for prosthetic and orthotic devices. Further, the compact design of the present invention allows it to remain laterally contained within the perimeter structure of the pivoting members of the joint with which it is associated where it is protected from and less likely to fail as a result of unwanted contact with surrounding objects.
While the description herein provides preferred embodiments of the present invention, it should not be used to limit its scope. For example, variations of the present invention, while not shown and described herein, can also be considered within the scope of the present invention, such as variations in the length or diameter dimensions of the piston, the thickness dimension and configuration of the resilient bumper, the number of bumpers used, the material from which the bumper or bumpers are made, the configuration of the central portion of the piston that interacts with the retaining pin for piston retention within the bore, the diameter dimension of the retaining pin, whether threads are used to secure the retaining pin in its usable position, and the end configuration of the retaining pin that could be designed to allow insertion of a tool therein to provide easy removal of the retaining pin for access to the piston and bumper. Thus the scope of the present invention should be determined by the appended claims and their legal equivalents, rather than being limited to the examples given.